Professional Experience: Ministry of Foreign Affairs, Thailand (1986-2017): Chief Legal Counsel in maritime delimitation negotiations (1986-2017), Director, Division of Legal Affairs, Department of Treaties and Legal Affairs (1999-2002), Deputy Director-General, Department of Treaties and Legal Affairs (2002-2004), Ambassador responsible for international legal issues and counter-international terrorism (2004-2006), Director-General of the Department of International Organizations (2006-2007), Ambassador to Iran (2007-2010), Australia, Fiji, Papua New Guinea, Solomon Islands and Vanuatu (2010-2012), Ambassador to the Russian Federation, Armenia, Belarus, Moldova and Uzbekistan (2015-2017); delegate and Secretary to the President, Inter-Sessional Meeting, Asian-African Legal Consultative Committee, New Delhi (1987); delegate and subsequently head of delegation, Preparatory Commission for the International Sea-Bed Authority and for the International Tribunal for the Law of the Sea, 5th to 9th sessions (1987-1991, Chairman, Group of 77 of the Whole, 1991); adviser, land boundary negotiations with Malaysia, Burma (Myanmar) and Laos (1987-1994); delegate, fisheries negotiations with Malaysia (1988-1993); delegate, fisheries co-operation negotiation with Vietnam (1991); delegate, UN Environment Programme’s Intergovernmental Conference to Adopt a Global Programme of Action for the Protection of the Marine Environment From Land-Based Activities, Washington, DC (1995); Visiting Professor, University of New South Wales School of Law, Sydney (1999-2008); head of delegation, 5th and 8th Sessions of the Preparatory Commission for the International Criminal Court (2000, 2001); Visiting Professor, Asia-America Institute in Transnational Law, Duke University School of Law (2000 and 2004); listed as expert for the purposes of special arbitration under art. 2, Annex VIII, of the Convention (2000-2014); head of the Thai delegation, 40th Session, Asian-African Legal Consultative Organization, New Delhi (2001); alternate representative, UN General Assembly (2001, 2007); advisor and agent in two cases before the International Tribunal for the Law of the Sea (2001 and 2013-2015); head of delegation, UN Open-ended Informal Consultative Process on Oceans and the Law of the Sea, New York (2001, 2011, 2013); eminent adviser, Constitutional Court of Thailand (2006); alternative representative, Steering Committee of the Four Nations (Chile, South Africa, Sweden and Thailand) Initiative on Governance and Management of the UN Secretariat (2006-2008); Distinguished Visitor (equivalent to a visiting professor), National University of Singapore Faculty of Law (2006, 2009); representative, UN General Assembly (2006-2016); Chairman, Working Group on the Administration of Justice at the UN, Sixth Committee, UN General Assembly (2011); Executive Director of the Thailand Trade & Economic Office (2012-2015); Chair, Expert Consultation on Thailand’s Implementation of UNCLOS and Related Instruments, Bangkok (2013); delegate, meetings of the Ad Hoc Open-Ended Working Group to study issues relating to conservation and sustainable use of marine biological diversity beyond areas of national jurisdiction (2014-2015); President, 25th Meeting of States Parties to the UN Convention on the Law of the Sea (2015-2016); delegate, Preparatory Commission on the development of an international legally binding instrument under the UN Convention on the Law of the Sea on BBNJ (2016-2017); regular speaker and panellist at international seminars, conferences and workshops on the law of the sea; Conciliator under Annex V to the Convention (July 2017–present); Arbitrator under Annex VII to the Convention (July 2017–present); Visiting Research Consultant, Centre for International Law/National University of Singapore (April 2018-March 2019); Visiting Research Fellow of the University of Oxford's Mansfield College and Bonavero Institute of Human Rights (Hilary & Trinity Terms 2018); Presiding judge of the world grand finale round of the Price Media Law Moot Court Competition 2018.

Member: Chairman, Foundation for the Development of International Law in Asia (1999-2006); Editorial Board, Asian Yearbook of International Law (1999-2006); UNESCO Intergovernmental Oceanographic Commission’s Advisory Body of Experts on the Law of the Sea (1999-2004); Regional Network on the Legal Aspects of Marine Pollution under the UNDP/IMO Programme for the Prevention and Management of Marine Pollution in the East Asian Seas (1995-2010); Advisory Panel (International), Indian Journal of International Law (2005-2012); Global Associate, Centre for International Law/National University of Singapore (2009-present); UN International Law Commission (2012-2016); Eminent Persons Group of the Asian-African Legal Consultative Organization (AALCO) (2012-present); Advisory Board, Thailand Journal of International Law (2015-present).

Publications: Published widely in the field of the law of the sea and other fields of international law, including: The Law of the Sea and Maritime Boundary Delimitation in South-East Asia, Oxford UP, 1987; Regional Co-operation on the Law of the Sea: ASEAN and the EC Perspectives (ed.), International Studies Centre, Institute of Foreign Affairs, Bangkok, 1988; Deep Seabed Mining and Its Reflections on Contemporary International Law, International Studies Centre, Institute of Foreign Affairs, Bangkok, 1989; “Development of ocean law and policy and management in Thailand”, Marine Policy 315, 1990; “Marine Resources Management”, 8 Foreign Relations Journal 83, Philippine Council for Foreign Relations, 1993; “Using Trade Sanctions and Subsidies to Achieve Environmental Objectives in the Pacific Rim”, 4 Colorado Journal of International Environmental Law and Policy 296, 1993; “Effectuation of international law in the municipal legal order of Thailand”, 4 Asian Yearbook of International Law, 1994; “Trade And The Environment In Pacific Rim Nations”, American Bar Association, Standing Committee on Environmental Law, Washington, DC, 1994; Research Report to Thailand’s Law Reform Committee on Development of The Legislation on the Continental Shelf and the Exclusive Economic Zone (in Thai), Bangkok, 1995; “Practical Difficulties for the International Criminal Court to Overcome”, in: Proceedings of the 6th Annual Conference of the Australia-New Zealand Society of International Law, Canberra: Australian National University, June 1998; “International Legal Order in a Changing World”, in: Proceedings of the International Law Association-Australia/New Zealand Society of International Law Conference: Wellington, July 1999; “The NATO Military Action and the Potential Impact of the International Criminal Court”, 4 Singapore Journal of International and Comparative Law, 2000; International Criminal Law, Oxford UP, 2001; “A Code of Conduct for Human and Regional Security around the South China Sea”, 32 Ocean Development & International Law 131, 2001; “International Criminal Law”, in the Diplomatic Training Programme Manual, University of New South Wales, Feb. 2002; “A century of challenges for international law”, Brazilian Society of International Law Bulletin – Centenary Edition, December 2017; Public International Law of Cyberspace, Springer 2017; The Obligation to Extradite or Prosecute, Oxford UP (March 2018); 'International Humanitarian Law and the Asia-Pacific struggles for national liberation’ in Asia-Pacific Perspectives on International Humanitarian Law (eds. Suzannah Linton, Tim McCormack and Sandesh Sivakumaran (Cambridge University Press 2019).